1. Field of the Invention
The present invention relates to a multilayered ceramic capacitor, a mounting structure of a circuit board having the multilayered ceramic capacitor mounted thereon, a packing unit for the multilayered ceramic capacitor.
2. Description of the Related Art
A multilayered ceramic capacitor, a multilayered chip electronic component, is a chip-type condenser commonly mounted on the printed circuit boards of various electronic products, such as image display devices including a liquid crystal display (LCD) and a plasma display panel (PDP), computers, personal digital assistants (PDAs), mobile phones, and the like, implementing charging and discharging of electricity therein.
Multilayered ceramic capacitors (MLCCs) may be used as components of various electronic products due to a small size, high capacitance, and ease of mountability.
A multilayered ceramic capacitor may have a structure in which a plurality of dielectric layers and a plurality of internal electrodes having different polarities and having the dielectric layers interposed therebetween are alternately laminated with each other.
Since the plurality of dielectric layers have both piezoelectric and electrostrictive properties, a piezoelectric phenomenon may occur, causing vibrations among the internal electrodes when AC or DC voltage is applied to the multilayered ceramic capacitor.
Such vibrations may be transferred through external electrodes of the multilayered ceramic capacitor to a printed circuit board on which the multilayered ceramic capacitor is mounted, and the entire printed circuit board may become an acoustic reflection surface generating sound from the vibrations.
The sound generated by the vibrations may correspond to an audible frequency within the range of 20 to 20000 Hz, and this vibrating sound, frequently causing an unpleasant feeling in people is known as acoustic noise.
In order to reduce acoustic noise, products in which a lower cover layer of the multilayered ceramic capacitor is enlarged have been researched.
In addition, a multilayered ceramic capacitor having a thickened lower cover layer may be mounted on a printed circuit board in a horizontal manner, while the thickened lower cover layer is located below, which may help in reducing acoustic noise.
Here, an image recognition method or the like is used to differentiate directions in which the thin upper cover layer and the thicker lower cover layer of the multilayered ceramic capacitor are mounted. However, the image recognition method or the like requires an excessive amount of cost and time and thus, assembly efficiency of the mounting substrate may be deteriorated.
In the Related Art Documents below, Patent Document 1 fails to disclose a dummy electrode, while Patent Document 2 fails to disclose a lower cover layer thicker than an upper cover layer.